LEND H-18: incorrect `srcEid` check in `borrowWithInterest` (cross-chain debt reads 0 → liquidation evasion)

Source & credit. Reproduction of a public audit finding curated by AuditVault — the original finding: 58387-h-18-incorrect-srceid-check-in-borrowwithinterest-sherlock-l. Standalone Foundry PoC and full write-up: 58387-h-18-incorrect-srceid-check-in-borrowwithinterest-sherlock_exp in the evm-hack-registry mirror.

Vulnerability classes: cross-chain · wrong-endpoint-id-field · liquidation-evasion · accounting-under-report

Reproduction: a faithful minimal reproduction of LendStorage.borrowWithInterest (Sherlock 2025-05-lend-audit-contest, commit 713372a1). The vulnerable function is reproduced verbatim (marked @>); the lToken interest index and the liquidation gate are faithful minimal doubles. Local deploy, no fork.

Root cause#

LendStorage.borrowWithInterest sums a borrower's cross-chain debt on the current chain. When a cross-chain borrow is stored on the source chain (Chain A), the record's fields are set to srcEid = ChainB (the destination) and destEid = ChainA (the current chain). But the filter uses the wrong field:

SOLIDITY

Borrow[] memory borrows = crossChainBorrows[borrower][_token];
...
for (uint256 i = 0; i < borrows.length; i++) {
    if (borrows[i].srcEid == currentEid) {                         // @> wrong field
        borrowedAmount +=
            (borrows[i].principle * LTokenInterface(_lToken).borrowIndex()) / borrows[i].borrowIndex;
    }
}
return borrowedAmount;

borrows[i].srcEid is ChainB, and currentEid is ChainA, so the condition is never true on the source chain. Every real cross-chain borrow is skipped and borrowWithInterest returns 0.

Impact#

Cross-chain debt is invisible. An account with a real cross-chain borrow reads as having zero cross-chain debt, so getHypotheticalAccountLiquidity treats it as over-collateralized.
Liquidation evasion → bad debt. An underwater cross-chain borrower cannot be liquidated (the liquidation path sees no debt), so the protocol eats the loss. The same under-report also lets the borrower draw further borrows against phantom capacity.
In the PoC, a 1,000-token underwater borrow reads as 0; the liquidation attempt no-ops and the borrower retains the full 1,000-token principal.

Attack walkthrough#

flowchart TD A["Chain A record: srcEid = ChainB, destEid = ChainA (= currentEid)"] --> B["borrowWithInterest iterates borrows"] B --> C{"borrows[i].srcEid == currentEid ?"} C -->|"ChainB == ChainA → false"| D["borrow skipped"] D --> E["borrowedAmount = 0"] E --> F["account looks healthy → liquidation no-ops"] F --> G["underwater borrower keeps the 1,000-token principal"]

PoC#

Registry (Foundry, local deploy — exploit path + a fixed-filter control):

BASH

cd 58387-h-18-incorrect-srceid-check-in-borrowwithinterest-sherlock_exp
forge test -vv

Expected: test_attacker_evadesLiquidation PASS (reported debt 0 vs a real 1_000e18 borrow; principal retained) and test_control_fixedReportsDebtAndLiquidates PASS (fixed destEid == currentEid filter reports the real 1_000e18). The browser EVM Playground is served at /hacks/58387-h-18-incorrect-srceid-check-in-borrowwithinterest-sherlock/.

Remediation#

Filter cross-chain borrows on the source chain by destEid == currentEid, matching how the records are actually stored:

DIFF

-    if (borrows[i].srcEid == currentEid) {
+    if (borrows[i].destEid == currentEid) {

References#

Sherlock 2025-05-lend-audit-contest, issue #831: https://github.com/sherlock-audit/2025-05-lend-audit-contest-judging/issues/831
Vulnerable code: https://github.com/sherlock-audit/2025-05-lend-audit-contest/blob/713372a1ccd8090ead836ca6b1acf92e97de4679/Lend-V2/src/LayerZero/LendStorage.sol#L478-L503

Sources & further analysis#

Reproductions & code

Standalone PoC + full trace: 58387-h-18-incorrect-srceid-check-in-borrowwithinterest-sherlock_exp (evm-hack-registry mirror).
AuditVault finding: 58387-h-18-incorrect-srceid-check-in-borrowwithinterest-sherlock-l.
Upstream DeFiHackLabs PoC directory: src/test.

Alerts & third-party analyses

DeFiHackLabs incident explorer: search "LEND H-18: incorrect srcEid check in borrowWithInterest (cross-chain debt reads 0 → liquidation evasion)".
Web3Sec X hacked database: search.
Rekt leaderboard: search.
Solodit incident search: search.

These dashboards index community alerts tweets, post-mortems, and independent write-ups. Reach them through the protocol name above to cross-check this reproduction against other analyses.

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